There have been several other bugs in this same dialog, some of them fixed wrt. updating the 'Save' insensitivity state when something changes that can be saved.

Loaded a local appointment in 1 local calendar, moved it to another local calendar by clicking the button: 'Save' didn't become sensitive, dismissed the dialog - it knew that there were unsaved changed: interesting :-)

I'd also suggest that each field that can be changed here is changed by whomever tests the fix to ensure that they all work correctly with the 'Save' button state update :-)